mineral

Selenite

Gypsum (Calcium Sulfate Dihydrate) - CaSO4·2H2O

AI-generated identification · may be incorrect

Hardness: 2 on Mohs scale (can be scratched by a fingernail). Color: Colorless to white, often transparent or translucent. Luster: Vitreous to pearly on cleavage surfaces. Crystal structure: Monoclinic; often found in bladed, tabular, or massive forms with perfect basal cleavage. Specific Gravity: 2.3.

Hardness: 2 on Mohs scale (can be scratched by a fingernail)
Color: Colorless to white, often transparent or translucent
Luster: Vitreous to pearly on cleavage surfaces

Identified April 20, 2026More mineral →

Explore Selenite in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed as an evaporite mineral in sedimentary environments, specifically in salt flats, hot springs, and caves where mineral-rich water evaporates. It can form over millions of years as saline waters concentrate.

Uses & applications

Used in the manufacture of plaster of Paris, wallboard (drywall), soil conditioners, and as a filler in paper and paints. Transparent varieties are highly valued by mineral collectors and used in ornamental carvings and metaphysical practices.

Geological facts

Selenite is named after the Greek word for the Moon, 'selēnitēs', because of its moon-like pearly glow. The world's largest crystals are selenite, found in the Cave of the Crystals in Naica, Mexico, reaching lengths of over 30 feet.

Field identification & locations

Identification: It is extremely soft (scratchable with a thumbnail) and has a distinct fibrous or sheet-like cleavage. Found globally, with notable deposits in Mexico, Morocco, and the USA (Utah/New Mexico). Collectors should look for its transparency and fragility.